Forecasting the Cosmological Constraints with Anisotropic Baryon Acoustic Oscillations from Multipole Expansion

TL;DR

This paper investigates how anisotropic baryon acoustic oscillations, analyzed through multipole expansion of galaxy power spectra, can effectively constrain cosmological parameters, with the hexadecapole spectrum providing significant additional information.

Contribution

It introduces a method to extract cosmological information from lower-multipole spectra, reducing reliance on full 2D spectra while accounting for non-linear effects and redshift distortions.

Findings

Monopole and quadrupole spectra alone slightly degrade constraints.

Hexadecapole spectrum significantly improves parameter constraints.

Constraints from combined multipoles are comparable to full 2D spectrum analysis.

Abstract

Baryon acoustic oscillations (BAOs) imprinted in the galaxy power spectrum can be used as a standard ruler to determine angular diameter distance and Hubble parameter at high redshift galaxies. Combining redshift distortion effect which apparently distorts the galaxy clustering pattern, we can also constrain the growth rate of large-scale structure formation. Usually, future forecast for constraining these parameters from galaxy redshift surveys has been made with a full 2D power spectrum characterized as function of wavenumber $k$ and directional cosine $\mu$ between line-of-sight direction and wave vector, i.e., $P(k,\mu)$. Here, we apply the multipole expansion to the full 2D power spectrum, and discuss how much cosmological information can be extracted from the lower-multipole spectra, taking a proper account of the non-linear effects on gravitational clustering and redshift distortion. The Fisher matrix analysis reveals that compared to the analysis with full 2D spectrum, a partial information from the monopole and quadrupole spectra generally degrades the constraints by a factor of $\sim1.3$ for each parameter. The additional information from the hexadecapole spectrum helps to improve the constraints, which lead to an almost comparable result expected from the full 2D spectrum.